Pad of silica-gel

The solution was filtered through a pad of silica gel to remove the catalyst and the filter residue was washed with methanol. The solvent was removed under reduced pressure using a rotary evaporator (water bath at 30 °C) to give a slightly brown oil. 

The molybdenum complex 1 (342 mg, 0.45 mmol, 1%) is added to a mixture of dichloromethane (90 mL), 1-octene (5.0 g, 44.6 mmol) and styrene (9.29 g, 89.2 mmol). The resulting mixture is stirred at room temperature for 1 h and then filtered through a pad of silica gel. After rinsing with dichloromethane the combined filtrates are concentrated and the crude product is purified by column chromatography (silica gel). 7.9 g (94%) of the title compound is obtained as a colorless oil. 

For example, the (salen)Co(III) catalysts depicted in Figs. 11 and 12 have been isolated with concomitant purified copolymer by filtration of the polymerization solution through a short pad of silica gel (230-400 mesh) resulting in the metal catalyst being trapped on the pad and the copolymer solution eluted [33]. The (salen)Co(III) catalyst was recovered from the silica gel pad upon solubilization with a methanol solution of NaBF4. In this manner, the separated catalyst could be reused without significant loss in catalytic activity and the copolymer isolated with a metal residue of only 1-2 ppm. 

For the recyclability of catalyst 1, after completion of the oxidation of 4-methoxybenzyl alcohol, the reaction mixmre was treated with water (3 mL), and the organic layer, after drying (Na2S04) and GC analysis, was passed through a short pad of silica gel using ethyl acetate and hexane as eluent to afford analytically pure 4-methoxybenzaldehyde in quantitative yield. Evaporation of the aqueous layer afforded the copper complex 1 that was subsequently reused for the oxidation of 4-methoxybenzyl alcohol up to three times using fresh TEMPO whereupon no loss of activity was observed. 

The reaction mixture is filtered through a pad of silica gel, Florisil or Celite . The addition of an organic solvent such as Et20 may facilitate the operation. The filtered solution is concentrated, giving a crude that needs further purification because of the presence of periodinane 38. 

To a solution of the N-methoxy-N-methyl-2,8-bis(trifluoromethyl)-quinoline-4-carboxamide amide (10 g, 28.4 mmol) in anhydrous ether (100 ml) was added a solution of 2-pyridyl lithium (Pinder et al (J. Med. Chem. 1968, 11, 267)) [formed by addition of 2-bromopyridine (3.3 ml, 34.6 mmol) to a solution of butyl lithium (29.7 ml of a commercial 1.6 M solution, diluted with an equal quantity of ether) at -78°C] at -78°C. Analysis of the reaction by TLC after 10 min showed that no starting material remained. The reaction was allowed to warm to room temperature, then poured into aqueous ammonium acetate, and extracted with ether, the combined organic layers washed with brine and dried (MgS04). Filtration through a pad of silica gel using ethyl acetate-hexane (1 1) afforded 9.0 g (84%) of the crude 2,8-bis(trifluoromethyl)-4-quinolinyl-2-pyridinylmethanone. This was recrystallised from isopropyl alcohol to give the product as colourless needles, identical to that described in the literature (Hickmann et al. Pinder et al. Ohnmacht et al. and Adam et al. (Tetrahedron 1991, 36, 7609)). 

Dry organic phase over Na2S04, concentrate the filtrate, add DCM and purify by filtration through a short pad of silica gel. 

A stirred solution of diene 7 in anhydrous toluene (0.2 mM) under argon was heated to 110 °C (reflux), and 5-10 mol% G2 was added to the refluxing solution. Stirring was continued for 15 min, and then the flask was immersed in an ice bath. The reaction mixture was passed through a pad of silica gel, which was rinsed with CH2C12 and concentrated, and compound 8 was purified by flash chromatography. 

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